Au Pair World/Greataupair - have totally given up, after spending so much time emailing/skypeing with candidates who then disappear off the face of the earth without so much as a message.
Next, an agency, one that has been recommended here many times. We live in the sticks, in a rural village. We have a child with special needs. So the first two candidates' profiles say: City, not rural. Will not look after a child with special needs. I mean, it's not hard is it? You just have to look at what boxes have been ticked by a) me and b) au pair candidates and go 'ooh look, those are the same'. My five year old could do that. And for a lot less than 300 quid.
Should I persevere with the interweb? It took me a month to find our last au pair off au pair world and just don't have the time now!